Just a small test on bullet weight & meplat trimming...

[Charles E]

We've been all over the map on bullet sorting lately.

In one thread, I mentioned that I trim meplats, then point, then trim again.

The reason is the nose portion of some bullet brands are not all the same length. On that first trim, I have the trimmer set to just barely even up an average bullet. That means some are untouched, and some have a slightly heavier cut. After pointing, I trim again, and this too is a very light cut. I then sort bullets by meplat size, since I don't repoint to a needle point. This by eye with a loupe that has .001 gradations on it -- special to the typesetting industry...

OK, here is the interesting part. I just weighed three bullets, after the first trim. These were .338, 300-grain Berger hybrids. The first was so short it was untouched by the trimmer. It weighted 300.0 grains. The second was one of the "average" ones -- the meplat completely touched, but not quite even due to how little was removed. It weighted 300.0 grains. The third on was one that was trimmed up a bit deeper. It weighted 300.1 grains.

Then I weight 5 187 BIBs completely finished. Four weighed 187, +.1, -0.0 (resolution of the scale). One weighed .2 over. An untouched (no trimming, no pointing) weighed 187.1 grains

The scale is an older Denver Instrument Accurate Load IV.

Well, not very many bullets. For a number of reasons, I haven't weight-sorted bullets in the past. I guess I will for a while, to get better data. I still don't think it matters, but I'm curious... Certainly no need to weigh except for the finished bullet; it looks like we can take off 0.1 grain or less with trimming.

 

[jim1K]

I don't think that will hold with a 6mm bullet due to the jacket thickness and the larger diameter being pulled down to a point. I never found a .1 gr. difference in a 6.....jim

 

[4Mesh]

Charles,

I don't think the material trimmed off is even significant by weight. I am not so sure any of us own a scale capable of measuring what was removed. I know I do not. Mine will only do .001 grams (.02grain) and it isn't even close to capable. That is not to say you can't find out what it represents in group size, just, it ain't very much. (We have bigger fish to fry)

When I read again, I'm not sure what you're looking for. I mean, we know weight affects BC just as the shape does.

 

[Charles E]

Phil, I've been thinking about one of your posts:

Now express that as a percentage of what is the smallest measurable error on the target. Meaning for any given error, what does it take before I see it. Can I quantify 1gn variation in powder as vertical dispersion? Ok, how much is it. What % does my weighing accuracy represent? Ok now I know what I am giving up in powder weighing at my chosen resolution. There is not a doubt in my mind that 1 gn weight difference in otherwise identical bullets is easy to see at 1K. Is in my guns anyway. At that point, I figure that shooting .3gn difference in bullet weight, (altering BC) is worth a measurable vertical, and I'm not gonna do it. Now if someone else wants to, that's fine by me.

You started out with powder, but at the end, seemed to be talking about a 0.3 grain variance in bullet as significant.

OK, truth to tell, I've never weighed bullets. Just followed the old saw that yes, the heavier bullet has a slightly higher BC, but it also has a slightly lower velocity, and the two even out. OK, I realize that's a pretty stupid position -- it may be true generally (who knows abut the "even out"part?), but for *this* round...

Part of this is background. When I started shooting 1K in 1996, any 10 shot group less than 10 inches was a pretty good one. Often as not, an 7- to 8-inch group would win. Forget weighting or measuring bullets, unless they were Sierras or (some) Bergers or Hornadys... just shoot a custom bullet & forget about it.

That's no longer true, and I'm trying to adapt.

The other part is I figured out that the "shooting" portion of 1K is score, not group. Any shooter just needs some luck to win group, whether that be a superior barrel, good bench draw, whatever. Remember when people on BR Central use to argue about can you or can't you read the wind at 1,000 yards? Well, I'm on the "no" side if you're talking about groups less than 6-7 inches, and anything less than a strong wind. But score starts out out with a 7-inch cushion for 10s and a restraint of 13 inches for 9s. Half tens and half nines give you a pretty decent score of 95.That's about enough target area to give the better shooter an edge.

But I've seen the writing on the wall, so to speak, and am just going to have to start taking as much care with bullet prep as with case & powder prep. Started this last year, and it showed up.

So, why did I do the little test? Hmm. Weighing bullets? How much counts? Do you have to do it twice? That is, are there any conditions that would get masked by not weighing bullets before and after prep work, like there are with trimming and pointing? The little test I just did says "No." But I did it 'cause you were saying that .3 grains of bullet mattered...

 

[4Mesh]

Charles,
I changed gears so to speak, in that post because I went from the current conversation to an analogy more universally relational to the masses.

I'll try to give an example and then my reasoning for it. All the numbers here are hypothetical so don't quote me on the errors I state here. I'm just using it as an example, many of which can be found in other areas of reloading.

Forget the bullet weight, because as you point out, there's a theoretical self balancing act between the lighter bullet and extra velocity vs the heavier going slower with higher bc.

Let use powder. Ok, so, I am trying to determine how close to weigh my powder. 300WSM, 210, H4350. To read here, most people if told to check what error .1 gn charge difference makes, would load up 5 rounds each of 62.5, and 62.6, and go shoot em at 1K. Plot the shots or mark bullets, and look at the two groups formed alternating shots. One group is centered .200 higher than the other, and conclude this is lost in the noise.

I would take 5 rounds each, 61gn and 63 gn, shoot em alternating shots, and plot the centers of THOSE two groups. Now, divide that 4" vertical difference and come up with each .1gn is .200" vertical, and IIIIII would say at the wailing wall, "Gee, how many times have I wanted my group to be .200 smaller?". Well for me, it is pretty much every time.

Now, it's a safe bet that 2gn of powder is worth a whole lot more than 4", in any rifle used at 1K. The numbers speak volumes though. Any shooter trying to win, if shown that there is something to be gained, WILL do the work to gain it. Now, show me something that you cannot quantify, like a "tuner". Nobody can make a gun shoot better, all they can do is make em worse. Ok, well, I'm not convinced then. Worse yet, they also can't tell you in plain english what it does. It's all voodoo. I'm not into working with voodoo. I like to see repeatable tests, and go from there. I also like to be able to amplify the error and single out the effect, rather than trying to find a .050 @ 1K error amongst 20 1" errors. Am I still interested in the .050 @ 1K error? Sure, just, not till I fix the 20 1" errors. If I have determined that error exists, and know what it does for me on the target to fix it, then I decide if it is worth my time in the current rifle, current conditions, etc. Sometimes the answer is yes, other times no.

Now, if I were you, I'd make some bullets light and go shoot a alternating shot test with heavy vs light. All else as close as ya can make em. Now, at 1K, does it really fix itself or not? I'd say 2 gn difference ought to show it. At that point, you may find yourself saying .1 gn bullet weight means nothing on the target. Fine, but do so after you test it. Then too, that does not excuse you from weighing the bullets cause in reality (for this sorting process), you are not looking for the ones that are .1 apart, you are looking for the outliers.

Lastly, as Harold Vaughn showed everyone in his book, just cause you fixed a 1" problem does not mean the group gets better by 1". The more errors you have, the less likely they are to show changes and be obvious about it. That is why his testing method was to grossly amplify the error condition so as to make quantification easier. Math is easy after the fact.